1. Field of the Invention
The present invention relates to reflective decorative laminates, and more particularly to such laminates as are useful in applications requiring exposure to mechanical stress and environmental extremes.
2. Description of the Prior Art
A variety of decorative, reflective laminates prepared with a variety of resin materials, have been developed and in existence for some time. With the increasing concern for safety and weight reduction, that has developed in the automotive industry, for example, the use of such reflective laminates in place of reflective articles prepared entirely from metal, has been on the increase. Thus, structures such as bumpers, side trim, grill work and the like, previously prepared from relatively rigid and heavier chromium-plated metals, are being replaced by the lighter weight resinous materials.
While wide-spread employment of resinous materials exists, their use has been primarily in the instance where pigmented non-reflective hardware such as bumpers, and the like, is acceptable in the design of the vehicle. In those instances where reflective surfaces are desired, however, the manufacturers tend to continue their use of the conventional plated metal, because they find that the reflective surfaces prepared from resinous laminates tend to be of inferior brightness and reflectivity, and frequently exhibit surface defects when exposed to mechanical impact, as well as deterioration of the metallic layer after relatively short exposure to atmospheric air and sunlight.
A variety of laminates specifically designed for automotive application have been developed, all of which have attempted to remedy the aforementioned deficiencies, by providing, in pertinent part, a reflective metal layer, usually vapor deposited upon a transparent resin film, with the resulting metal coated film bonded adhesively to one or more further resin films, so that the metal layer is presumably securely disposed within the resulting laminates. Variations on this construction are illustrated in the following U.S. Pat. Nos. 4,275,099; 4,235,949; 4,101,698; 3,811,989; and 3,720,567. Naturally, the foregoing listing is illustrative only, as other patents, and related publications illustrate yet further variations in construction and preparation of such laminates.
Of the patents listed, U.S. Pat. No. 4,275,099 to Dani is of particular interest, as it discloses in its general discussion, a laminate construction that is presently popular, that of the tri-laminate. Dani describes this construction as essentially three-ply, constituted of an aluminized polyester film, adhesively bonded to outer polyvinylfluoride film and bonded on its opposite side to a base layer of what patentee terms a "virgin vinyl resin." The patentee states further, that the tri-laminate maybe either heat fused or otherwise adhesively bonded to a three dimensional extrusion, to form products such as automotive trim strips and the like.
The deficiencies of this state of the art construction are also noted by Dani, in that patentee remarks that the laminated products tend to delaminate in use after relatively short exposure to outside environments. Dani notes that delamination frequently occurs at the adhesive interface between the metallized surface and the next adjacent resin film, and proposes a specific adhesive formulation that purportedly remedies this defect.
In addition to those deficiencies noted by Dani, the present inventors found that the commercial production of the known tri-laminates was exceeding difficult if not impossible, when attempts were made to adapt these tri-laminates to the preparation of automotive accessories by thermo forming techniques. Thus, it was observed that when the temperatures of the thermo forming operation fluctuated outside illustrative tolerances of about 5.degree. F., the resulting products exhibited surface crazing, the development of a haze in the resin films that reduced brightness and reflectivity, and an effect known as "rainbow," i.e., a multi-color hue that appears due to the distortion of the polyester film during the thermo forming process. Further, the appearance of any of the foregoing defects would result in the rejection by automobile manufacturers of products having these defects.
A further problem, noted by Dani, and others in the art, comprises the susceptibility of the resin laminate to attack and rapid deterioration upon exposure to ultra-violet light. Dani proposes to include an ultra-violet inhibitor in the polyester film to remedy this defect. The present inventors have found, however, that the adhesive utilized in the laminates presently known, have generally low resistance to deterioration from exposure to ultra-violet light, and therefore fail within an unacceptably short period of time after their installation. Further, the prior art adhesives appear to attack the adjacent metal layer and to cause it to corrode, with the result that desired appearance and laminate integrity rapidly deteriorate.
A need therefore exists for the development of an improved laminate and associated method of preparation that can efficiently and economically cure the noted product deficiencies.